The liver is the largest organ in the body and plays central roles in metabolisms in the body. The liver is the only organ in the body to be able to regenerate. It is known that even if 80% of the total liver weight is excised, the liver restore its capacity to the original weight.
At present, it is thought that the most effective method of treating serious chronic liver disorders, such as hepatitis C or liver cirrhosis which hinders functional liver regeneration, is a method of liver transplantation, in which a liver is transplanted from a liver provider (hereafter “donor”). Even hybrid-type of artificial livers or cell transplantation therapies requires liver cells derived from a living body. As a result, a lack of donors represents a serious problem for these therapies. Furthermore post-transplantation rejection and tissue loss in donors are also serious problems to be solved for the application of these therapies.
Recently these problems have resulted in considerable attention being given to cell transplantation methods using embryonic stem cells (hereafter “ES cells”) as one of the therapeutic methods replacing organ transplantation. ES cells are cells established from blastocysts of a fertilized ovum and it is considered possible to induce such cells to differentiate into the various functional cells constituting an individual. Furthermore at the ES cell stage, cell surface antigen related to rejection can be modified. Consequently the efficient differentiation of ES cells into hepatocytes for use in cell transplantation is expected to solve various problems related to transplantation therapies such as donor shortage, rejection and tissue loss in the organ donor.